Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
  • B01J8/0285—Heating or cooling the reactor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
  • B01J8/0207—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid flow within the bed being predominantly horizontal
  • B01J8/0214—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid flow within the bed being predominantly horizontal in a cylindrical annular shaped bed
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D9/00—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D9/0006—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the plate-like or laminated conduits being enclosed within a pressure vessel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D9/00—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D9/0062—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by spaced plates with inserted elements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/02—Header boxes; End plates
  • F28F9/026—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits
  • F28F9/0263—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits by varying the geometry or cross-section of header box
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
  • B01J2208/00017—Controlling the temperature
  • B01J2208/00106—Controlling the temperature by indirect heat exchange
  • B01J2208/00115—Controlling the temperature by indirect heat exchange with heat exchange elements inside the bed of solid particles
  • B01J2208/0015—Plates; Cylinders

Definitions

• the invention relates to the field of isothermal chemical reactors equipped with an internal plate heat exchanger.
• the invention is applicable, for example, to isothermal or pseudo- isothermal chemical reactors for exothermic or endothermic heterogeneous reactions, wherein the internal heat exchanger is immersed in a catalytic layer, or to reactors where the internal heat exchanger, in operation, is immersed in a fluid.
• Isothermal or pseudo-isothermal chemical reactors are reactors equipped with an internal heat exchanger adapted to maintain the temperature of the reaction in a range of optimal efficiency, by providing or removing heat from the reagents.
• Isothermal reactors are widely used, for example, in methanol synthesis plants, where the reactor comprises an internal cooling heat exchanger to remove heat generated by the exothermic methanol synthesis reaction.
• Isothermal reactors equipped with a plate heat exchanger are known to provide many advantages.
• the term "plate reactor”, in the following description, is used with reference to a chemical isothermal (or pseudo- isothermal) reactor equipped with at least an internal plate heat exchanger.
• a plate reactor is disclosed for example in EP-A- 1284813.
• the heat exchange elements are in the form of box- shaped flattened bodies, comprising two substantially rectangular walls, connected with each other at least along the perimeter, so as to define an internal chamber or passage where a heat exchange fluid (e.g. water or steam) is circulated.
• the plates are supported inside the reactor with known means, and are connected to appropriate means for feeding and collecting the heat exchange fluid.
• Differently structured plates are known in the art, including the so-called “swelled" plates, formed by two flat metal sheets joined by a perimeter welding and other welding points, and subjected to high pressure hydraulic swelling for obtaining the internal chamber between the two sheets.
• the internal plate heat exchanger is often formed as a substantially annular unit, with radial plates converging towards the axis of the reactor.
• the plates of the heat exchanger are arranged with long sides parallel to the vertical axis of the reactor, and radial short sides converging towards the same axis; cylindrical pipes are fixed to the bottom and top short side of each plate, to feed and collect the heat exchange fluid.
• the means for feeding and collecting the heat exchange fluid of annular heat exchangers often comprise radial pipes or ducts aligned with short, radial sides of the plates.
• said cylindrical pipes for the heat exchange fluid have diverging ends, namely the external ends lying on an external diameter of the annular structure of the heat exchanger itself, and converging ends, namely the opposite ends lying on an internal diameter of the same, near the axis of the chemical reactor.
• the spacing between the plates depends on various design parameters but, as a general rule, plates are relatively close together in order to increase the ratio between heat exchange surface and overall volume of the exchanger. Hence, the converging ends of said radial pipes can interfere each other or, in any case, the interspace between converging ends may become too little, causing some practical disadvantages, such as obstacle to discharge or refill the catalyst. To solve this problem, the prior art discloses solutions as shown in Figs. 5 and 6.
• plates 100 of an annular plate heat exchanger have fluid collectors 101, fixed to their short sides. Inner ends of collectors 101 converge in a zone 112, near the central axis of the reactor. As shown, to avoid interference between collectors 101 in said zone 112, plates 100 are disposed on two levels, so that the collectors 101 are alternatively lying on an upper and a lower plane. In exceptional cases, more than two levels can be used. This solution however has the drawbacks of a more complex and expensive construction.
• FIG. 7 another prior- art solution is shown, where plates 100 have angular cuts (or chamfers) 113 to keep the converging ends of collectors 101 distanced from the axis of the reactor (i.e. lying on a greater diameter) and hence avoid interference.
• This solution however is not always fully satisfying: the plates are more difficult to realize and the fluid flow inside is disturbed by cuts 113; moreover a transversal flow must be allowed inside the plates, in order to equalize the outlet flow and compensate for presence of said cuts 113.
• the problem underlying the present invention is to provide appropriate spacing, and avoid mechanical interference, between internal ends of radial heat exchange fluid feeding or collecting ducts of radial heat exchange plates installed inside isothermal chemical reactors.
• a chemical isothermal reactor comprising at least one plate heat exchanger with a substantially annular structure, said heat exchanger comprising a plurality of radially-arranged heat- exchange plates, and at least one set of radial ducts for feeding or collecting a heat exchange fluid to/ from internal passage(s) of said plates, said radial ducts being aligned with radial sides of the plates, said radial ducts having diverging ends and opposite converging ends due to their radial arrangement, said reactor being characterized in that the converging ends of radial ducts of said at least one set of radial ducts have a reduced cross section compared to the respective diverging ends.
• the invention also relates to a plate heat exchanger for use in isothermal chemical reactors, said heat exchanger comprising a plurality of radially-arranged heat-exchange plates, and at least one set of radial ducts for feeding or collecting a heat exchange fluid to /from internal passage(s) of said plates, said radial ducts being aligned with radial sides of the plates, said radial ducts having diverging ends and opposite converging ends due to their radial arrangement, said reactor being characterized in that the converging ends of said radial ducts have a reduced cross section compared to the respective diverging ends.
• the opposite converging and diverging ends of the radial ducts lie respectively on a first and second diameter of said annular structure, i.e. they are distributed over an inner and an outer circumference, having said first and second diameter respectively.
• Said radial ducts are the feeding ducts and/ or the collecting ducts of the heat exchange fluid.
• the radial ducts for the heat exchange fluid are fixed (e.g. welded) to short sides of the plates.
• the heat exchanger has opposite radial ducts for feeding and collecting the heat exchange fluid to/ from the heat exchange plates, e.g. upper and lower ducts in a vertical arrangement, and all of said opposite radial ducts have the converging ends with a reduced cross section compared to the respective diverging ends.
• the radial ducts are formed with reduced-cross section converging ends only at one side of the plates, preferably the fluid outlet side. This embodiment can be preferred when the outlet volumetric flow of the heat exchange fluid is significantly greater than the inlet volumetric flow, e.g. the fluid is at least partially evaporated through the plates.
• each radial duct or pipe has at least a tapered portion, where the cross section is continuously decreasing towards the inner, converging end of the duct. More preferably said tapered portion is conical or frusto-conical.
• the heat-exchange fluid ducts comprise a cylindrical portion and a tapered, preferably conical portion with a cross section constantly decreasing towards said converging ends; according to another embodiment, the ducts are tapered or conical for their whole radial length, from the outer diverging end to the inner converging end.
• the cone angle of conical ducts is preferably less than 10 degrees, more preferably between 10' (ten minutes of arc) and 5 degrees.
• said radial ducts of the heat exchange plates comprise a plurality of portions with different respective cross section, the portion near the converging end of each duct having a cross section smaller than the other portion(s) of the same duct.
• each of the radial ducts is realized with an outer cylindrical portion having a first diameter and a second inner portion, near the converging end, having a second diameter smaller than said first diameter.
• said ducts with reduced cross section at the converging ends are used in combination with heat exchange plates having a sandwiched structure, each plate comprising two walls and internal spacer elements, said spacer elements connecting said walls and defining internal channels for the heat exchange fluid, between the two walls.
• the invention solves the problem of the interference of feeding/ collecting ducts, as defined above.
• the invention is particularly advantageous when the heat exchanger is equipped with the sandwiched plates as defined above.
• Said plates have a strong resistance to a high pressure difference between inside and outside (such as 100 bars and beyond), and have been found to reduce internal pressure drop, so their use can be preferable in comparison, for example, to inflated pillow plates.
• a heat exchanger with sandwiched plates would require the expensive and complex arrangement of Fig. 6 to avoid interference of the internal ends of the fluid ducts, thus limiting the possible applications of these exchangers.
• the invention however can be used with any kind of heat-exchange plates, including the aforementioned inflated plates, maintaining the advantage of a correct spacing between the internal, converging ends of the fluid ducts, together with low cost and ease of installation.
• FIG. 1 schematically shows a partially cut-out view of an isothermal chemical reactor, according to a preferred embodiment of the invention.
• Fig. 2 schematically shows some details of Fig. 1.
• Fig. 3 is a cross section of one of plates of the exchanger inside the reactor of Fig. 1 , according to a preferred embodiment.
• Fig. 4 shows details of the plate and fluid duct of Figs. 1 and 2.
• Fig. 5 refers to another embodiment of the invention. Detailed description of preferred embodiments
• a radial-flow isothermal chemical reactor 1 which essentially comprises a vertical-axis cylindrical shell 2, a lower end 3 and an upper end 4, respectively with an inlet flange 5 for the fresh charge of reagents, and an outlet flange 6 for the products of a chemical reaction.
• the reactor 1 contains an annular catalytic rack, which is per se known and not described in detail, containing an appropriate catalyst and externally delimited by a cylindrical perforated wall 7.
• the reagents flow in a radial direction, from an interspace between the wall 7 and the shell 2, to a central collector 8 which is in communication with the outlet flange 6.
• the annular space defined by the catalytic rack is substantially the reaction space, where the reagents are converted into products.
• An axial-flow plate heat exchanger 10 is mounted inside the reactor 1, immersed in the catalyst.
• the heat exchanger 10 has substantially an annular structure, with radial plates 1 1 in the form of substantially rectangular box-shaped flattened bodies, having long sides 12i, 12e parallel to the axis of the reactor and radial short sides 13s, 13i. Plates 11 are connected to suitable distribution means of a heat exchange fluid, for example cooling water.
• a heat exchange fluid for example cooling water.
• the heat exchange fluid enters from lower sides 13i, flows axially inside the plates 11 and exits from upper sides 13s.
• the fluid is distributed via radial ducts connected to the plates 11 in an appropriate way; in the example the fluid is distributed via a set of radial pipes 14 fixed to the lower sides 13i of the heat-exchange plates 11, and collected by a set of radial pipes 15 fixed to the upper sides 13s.
• Each plate 11 is equipped with a respective distributor pipe 14 and a respective collector pipe 15.
• the fluid is fed via a piping system comprising an inlet flange 20, a pipe 21, and another annular pipe 22, feeding the distributor pipes 14. Fluid passes from each of said distributor pipes 14 to the inside of the respective plate 11 for example by holes or slits of the pipe 14, which are known per se.
• the collector pipes 15 receive the fluid from plates 11, and are connected to an annular pipe 23 and to an exit flange 24.
• the pipes 14 and 15, due to their radial arrangement inside the reactor 1, have diverging ends 14d and 15d arranged on a first circumference having a first diameter slightly less than diameter of wall 7, and opposite converging ends 14c and 15c arranged on a second circumference having a second diameter slightly greater than the diameter of the central duct 8. Said first diameter is substantially equal to the external diameter of the annular heat exchanger 10, while said second diameter is substantially the internal diameter of the same annular structure.
• the distributor pipes 14 and/ or the collector pipes 15 have a reduced cross-section at least near the converging ends 14c, 15c, in order to avoid interference and maintain a suitable spacing between the pipe ends.
• the pipes 14 and/ or the pipes 15 are preferably conical pipes as shown.
• conical collector pipes 15 are fixed on upper short sides 13s of plates 11, thus having converging ends 15c, near the axis of the reactor, with a smaller cross-section than the opposite ends 15d, and leaving a suitable spacing S between the pipe ends.
• each plate 11 essentially comprises two walls 31 and 32, parallel to each other, connected by internal spacers 33 defining channels 34 for the heat exchange fluid. Additional spacers can be provided along the longitudinal perimeter edges of the walls 31 and 32, for the lateral sealing of the plate 30.
• the walls 31 and 32 in a preferred embodiment, are formed from respective flat metal sheets, and the spacers 33 are represented by plate strips, of appropriate thickness equal to height of channels 34.
• the conical pipes 15 comprise openings or slits 40, each slit 40 being in fluid communication with at least one of said channels 34. Preferably there is one slit 40 for each channel 34.
• the distributors 14 can be realized in the same manner as collectors 15 above described. According to the invention, at least the heat exchange fluid distributors or the heat exchange fluid collectors have the reduced cross section at the converging ends.
• distributor pipes 14 and/or collector pipes 15 comprise portions with respective different cross sections.
• each of the pipes 15 comprises an outer cylindrical portion 15e having a first diameter, and an inner cylindrical portion 15f, near the converging end 15c of duct 15, said inner portion 15f having a second diameter smaller than diameter of the first portion 15e.
• the radial pipes 14 and/or pipes 15 comprise more than two portions, with the cross section decreasing from outer end to inner end of the pipe itself.
• the operation is as follows. Reagents are fed to reactor 1 by flange 5, and radially flow through the catalytic reaction zone, where the exchanger 10 is installed.
• a heat exchange fluid for example water, is fed to the plates 11, entering and exiting through flanges 20, 24 and related piping.
• the reduced-cross section converging ends 14c, 15c of pipes 14, 15, as seen in Fig. 1, avoid interference between the pipes and leave a suitable free space S (Fig. 2) between the pipes, useful for example to discharge/ re-feed the catalyst.
• the exchanger 10 cools the catalytic bed and the reaction products, maintaining the reaction temperature in an optimal efficiency range.
• the heat exchange fluid can be water which is at least partially evaporated inside plates 11.
• the provision of water/ steam collectors having a reduced-cross section at the converging ends is particularly advantageous.
• the invention is applicable to any kind of chemical reactor containing a plate heat exchanger, in particular to radial-flow, axial-flow or transversal-flow reactors.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Thermal Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Geometry (AREA)
• Fluid Mechanics (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

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• 2008
  • 2008-02-18 EP EP08002925A patent/EP2090355A1/en not_active Withdrawn
• 2009
  • 2009-02-13 US US12/918,024 patent/US9120068B2/en active Active
  • 2009-02-13 MX MX2010008712A patent/MX2010008712A/es active IP Right Grant
  • 2009-02-13 RU RU2010138279/05A patent/RU2482909C2/ru active
  • 2009-02-13 CA CA2714470A patent/CA2714470A1/en not_active Abandoned
  • 2009-02-13 WO PCT/EP2009/001046 patent/WO2009103461A1/en active Application Filing
  • 2009-02-13 EP EP09712958.9A patent/EP2244821B1/en active Active
  • 2009-02-13 AU AU2009217005A patent/AU2009217005A1/en not_active Abandoned
  • 2009-02-13 BR BRPI0908246-8A patent/BRPI0908246B1/pt active IP Right Grant
  • 2009-02-13 CN CN200980105341.2A patent/CN101952022B/zh active Active
  • 2009-02-16 AR ARP090100546A patent/AR070400A1/es unknown
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